With the advances in disk drive technology, the geometry of magnetic recording heads and corresponding data track pitch is continually becoming smaller. As the heads become smaller, the acceptable range of a head's writer width that can be used for a hard disk media surface with a static data track per inch (TPI) format becomes smaller as well. Thus, controlling the writer width to within a percentage tolerance becomes increasingly more difficult. As illustrated in FIG. 1a, a distribution 100 of typically available head writer width versus the probability of the available heads being acceptable for use in a hard drive is illustrated in FIG. 1a. As head writer widths vary from 0 to W, the probability ρ that a head will be acceptable within a hard drive attains a maximum probability P at head width wp. Usable heads have a width within a range of α, which contains the width having the highest probability. As illustrated in FIG. 1a, a range α of acceptable writer widths in a hard drive with a constant track per inch format exists around wp. Typically, the range a of acceptable writer widths is small, thereby limiting the number of manufactured heads that can be used in modern hard drives.
A hard drive system 150 in accordance with one embodiment of the prior art is shown in FIG. 1b. Hard drive system 150 includes a hard drive 121 with parts including a disk controller 118, microprocessor 120, servo controller 110, read/write channel 114, a preamp 116, voice coil motor 108, spindle motor 104, actuator 106, head 105 and disks 102. Hard drive 121 may send and receive information with host(s) 122. In a standard data write operation, data write information is received from host 122 by the disk controller 118. The data to be written is sent by the disk controller to read/write channel 114 and data write instructions are sent to microprocessor 120. The microprocessor sends a signal to the servo controller. The servo controller then sends signals to the voice coil motor 108 to position actuator 106 to the data track and sector of disk 102 to which the data is to be written. Once the data track and sector are selected and the head is aligned with the desired data track, a signal from the servo controller to the read/write channel, in one embodiment, enables a data write operation through the preamp 116 to the disk 102. Throughout write operations and similarly executed read operations, the spacing between data tracks is uniform.
Variable data TPI hard drive systems where data and servo TPI are chosen arbitrarily have been slow to evolve because they involve complicated software and mathematical processes. For this reason, variable data TPI methods are not very well developed in the electronic storage device industry. What is needed is a variable data TPI system and method that overcomes the limitations and disadvantages of the prior art.